1. Field of the Invention
The present invention generally relates to a semiconductor structure. In particular, the present invention is directed to a semiconductor structure for use in an image sensor with an oblique pick up plug enabling an alternative conductive path to dissipate electrons.
2. Description of the Prior Art
A semiconductor device is widely used in electronic apparatuses. For example, a camera including an image sensor is widely used in portable apparatuses, such as mobile phones.
Since lighter, thinner and smaller mobile phones are more popular, a desirable image sensor is the smaller the better. In addition, a smaller image sensor is at the same time required to have higher resolution to meet the market demands.
FIG. 1 is a cross-section view of an image sensor 9. The image sensor includes a P+ substrate 10, pixel regions 39 and P-type isolations 19. As shown in FIG. 1, when image sensor 9 is exposed to light, the pixel regions 39 serve as photo diodes to receive light and generate image signals by producing electrons 11. The generated electron holes 12 should be quickly dissipated to the ground via the p-type isolation 19 and the substrate 10. The p-type isolation 19 separates the pixels regions 39 apart.
One possible solution to shrink the image sensor and simultaneously to enhance the resolution is to scale down each cell unit in the image sensor. More specifically speaking, both the pixel regions and the p-type isolations need scaling down.
However, smaller p-type isolations 19 between the pixel regions 39 results in higher electric resistance of the p-type isolations 19 and worse device performance due to a reduced cross section. This is a trade-off between two extremes, namely better device performance and a smaller device size.